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  #91  
Old 04-21-2014, 07:45 PM
erich weaver's Avatar
erich weaver erich weaver is offline
 
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Location: santa barbara, CA
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"I fully rebuilt the airplane and have been flying it for about 5 years. It is based at an airport with a paved and a grass runway. I probably make 95% of my home base landings on the grass (cheapskate... like to save wear on tires), with the original version nose gear fork <gasp>. "

Classic! Thanks for your input to this thread.
Cant stop myself from asking though - I'm guessing you haven't installed the Antisplat nose job either?

Erich
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  #92  
Old 04-21-2014, 08:10 PM
NASA515 NASA515 is offline
 
Join Date: Nov 2011
Location: Hansville, Washington
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Default Over and out?

But, Scott, you have promised me a beer!

Well said, and I appreciate your perspective. After you buy me my beer, I'm committed to buy you one. In the end, we'll probably have too many beers and still disagree.

Oh well.....

Bob Bogash
RV-12
N737G
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  #93  
Old 04-21-2014, 08:33 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Quote:
Originally Posted by catmandu View Post
I have an updated nose gear leg, and installed all the Anti-Splat modifications. I am fanatical about technique on every movement of the plane to keep it light on the nose. I have insurance. I land on grass. I only hope not to tip over, may Forculus, god of the threshold, forever look kindly on my risk mitigation.
Wasn't Forculus the god of doors and Limentinus, god of the threshold?

My third wheel has fallen behind, so it acts differently. Hopefully it will behave.
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Bill

RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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  #94  
Old 04-21-2014, 10:06 PM
AV8AZ AV8AZ is offline
 
Join Date: Nov 2013
Location: Phoenix, Arizona
Posts: 60
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In my field (medicine) it is common knowledge that statistically I personally will cause personal harm to people who I am directly responsible for and may even cause early death in a few, despite my best efforts. We constantly try to mitigate risk and improve. We have a lot of room for improvement. Obfuscation and cult-think have no place in a serious discussion on safety. The first clouds the data and the second clouds the analysis. I might give some people a pass on understanding this, others not so much.

Back to the nose gear. We criticize auto-conversion engine folks for being tinkerers instead of fliers. We remind them that dinosaur technology works. I don't understand the logic of promoting tinkering with the current nose wheel setup when other systems have proven less problematic. If you don't agree with "proven less problematic" then I don't know what to say.

Tyson
PS: I would concede that any aircraft with a nose gear will eventually experience a nose gear failure. The question is about the statistics of the phenomenon. Like the 601XL issue, 'at all cost' designer-supporters seem to maintain a very similar 'no real problem' view. This is probably a dead horse as each reader is in one camp or the other.
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  #95  
Old 04-21-2014, 10:32 PM
RVnoob RVnoob is offline
 
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Location: London
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Quote:
Originally Posted by NASA515 View Post
With regard to data collection, I'm assuming everybody has seen and read the NTSB Special Structures Study on RV-6A thru -9A nose gear failures and resultant airplane flips. They analyzed 19 events in 2007. The study can be found here:

http://www.ntsb.gov/doclib/reports/2006/rv_study.pdf
::
We all have selective reading...
Quote:

3.0 SUMMARY:
::
The FEA shows that the nose gear strut has sufficient strength to perform its intended function. In all cases, the landing gear struts and forks were making contact with the ground and initiating the damage sequence.

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  #96  
Old 04-22-2014, 12:20 AM
jongurley jongurley is offline
 
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Location: North Carolina
Posts: 94
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Quote:
Originally Posted by rvbuilder2002 View Post
Well Bob, you may no longer be in your working years (though some of your posts I have seen, describing what you stay busy with in your retirement years makes it seem like you still are ), but your phrase still applies...

"I feel certain" does not constitute facts and data.
The reality is, Van's doesn't have a big data base of research done on A model flip-over accidents, and doesn't have any more information about most accidents than anyone else does that spent the time looking at what is available in the NTSB reports.

Occasionally, the NTSB requests assistance, but I think most of those instances have been fatal accidents where having someone very familiar with the engineering, and the structures is helpful.

The FAA has requested help with an RV-12 nose gear failure. As a result, some specific static load testing was done on a sampling of nose gear forks. Based on the data from those tests, the data that was acquired from the EFIS system in the accident airplane, and factored with photos of the touchdown (impact) points on a grass runway, they were fully satisfied that the accident was the result of pilot error. As I have already mentioned is most often the case, the pilots account of what happened didn't entirely match up with what all of the other data clear showed happened.

Since the release of the NTSB report you sited (almost 7 years ago now, and Van's contributed data and information to it), I am not aware of them having any interest in having another look at it.

So, in a nut shell, even if I was in a position to provide you with an answer to your questions, I wouldn't have any more data to give credible answers, than anyone else who has spent time researching in the NTSB report (no easy task).

One thing I would like to make clear (and then I am clearing out of this thread)...
I personally own an RV-6A.
I purchased it damaged, as a result of a flip over accident.
The accident was totally pilot error (and listed so in the NTSB final report)
Because of my communications with the original builder / accident pilot, I know some details of the accident that didn't even make it into the report.
So I have my own personal interest in the subject.

I said it once, but I will repeat it again, without some method of data collection outside of the account that the pilot or other witnesses can give, knowing what the actual cause of an accident like this is can be difficult. I am not saying that developing a process to gather data is not worth the effort, just saying that it will be of much less value if something to substantiate the personal account of what happened is not part of the report.

I fully rebuilt the airplane and have been flying it for about 5 years. It is based at an airport with a paved and a grass runway. I probably make 95% of my home base landings on the grass (cheapskate... like to save wear on tires), with the original version nose gear fork <gasp>.

No one at Van's has ever swept this under the rug, as some have been very vocal in proclaiming.
I think the attitude is more along the lines of being realistic (as Alan did a good job of saying earlier). The realistic attitude is that the airplanes are one big engineering compromise... with the goal of attaining the best (ultimate) performance possible.
Could the nose gear be more forgiving. Sure (and since that seems to be a good idea for a lot of the pilot population, the RV-14A was born), at the cost of simplicity and the balance of engineering compromises that exist right now.

As we know, RV's are experimental class airplanes. If an owner decides they don't like the way the different compromises align, they are free to align them a different way.

Comments have been made comparing an RV-6A to a C-150... keep in mind that an average empty weight C-150 (with a stink-en little O-200 on the front) is about the same as a lot of fixed pitch prop RV-6A's.

My personal feelings (as everything in this post is... what I said above is in no way speaking for Van's or anyone else who works there).

If someone has an interest in really getting to the bottom of this, and if they could objectively look through all of the accidents with enough data available to determine in which accidents it was simply a pilot having a bad day (I say if, because in a lot of them it is not possible), and then would focus on what is left, I believe it would look like a much smaller problem.


Over, and out!
This is the most important quote of the whole thread, all the "data collecting" everyone is wanting is fine and dandy, but with "pilot technique" in the equation there is no hard data to even remotely determine the causes. I bet out of a sample of 100 nose wheel accidents of any type of airplanes over half the pilots either didn't tell the truth about their error or didn't think they did anything wrong. Just like the RV accident i read on here about a year or so ago, "I brought it in to land and it bounced twice and then the gear collapsed", well OKKKK yeh it collapsed because you porpoised it in and put 10000lbs(or whatever) of force on the nosewheel. I just think there is alot of pilot error involved in a BIG percentage of these accidents and alot of people are wanting to blame the nose gear, but thats just my opinion. And if everyone wants a eye opener(and i am sure you guys have seen), go to sun n fun or oshkosh pull up a chair and just set there for hours watching landings, they will bounce and slam them in all day long. Heck it happens to everyone at one time or another and some pilots WAY more than normal if you catch my drift. Me and my partner are building a RV7A with no nosewheel worries

Last edited by jongurley : 04-22-2014 at 12:24 AM.
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  #97  
Old 04-22-2014, 05:51 PM
roadrunner20's Avatar
roadrunner20 roadrunner20 is offline
 
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Location: Bay Pines, FL (based @ KCLW)
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Quote:
Originally Posted by Jeff Vaughan View Post
I purchased a very early 7A kit in 2001. At that time Vans suggested the nose wheel version if you will be flying off of grass as the 7A will get off the grass quicker than the 7. This was actually promoted in their early 7 series literature.
I chose to build the 7A because I had no tail wheel time and I did want to fly off of grass. I completed my 7A and have not yet landed it on grass. A whimp?
Maybe but Vans no longer suggested the 7A is a better choice for grass. They changed their literature! hmmmmm
Did Van really say the 7A would get off quicker than the 7?

I converted my RV7A to a 7.
I can tell you right now the the TW gets off much quicker than my A model did.
I would questimate about 50 feet as I compare it to my windsock.
Unless, he just meant getting the nose wheel off the ground & not flying.

My home base is paved, not grass.
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Danny "RoadRunner" Landry
Morphed RV7(formally 7A), N20DL, PnP Pilot
1190+ hours
2019 Donation Paid

Last edited by roadrunner20 : 04-22-2014 at 05:57 PM.
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  #98  
Old 04-22-2014, 06:27 PM
Jeff Vaughan's Avatar
Jeff Vaughan Jeff Vaughan is offline
 
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Sure did. if you have the old literature it is there. I recall the their reasoning behind this was the angle of attack of the 7A vs the 7. Maybe it is Pilot technique!
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  #99  
Old 04-22-2014, 07:04 PM
sailvi767 sailvi767 is offline
 
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Location: Charlotte NC
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The AOA would have no bearing on takeoff. With a tailwheel you can set the AOA at any level you are comfortable with at liftoff. You can even leave the tailwheel on the ground to generate the highest AOA and shortest ground roll. You could try and do that with a nose gear by rotating early but would be within inches of dragging the tail to match the tailwheel aircrafts attitude. There must be another factor at play here.

George
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  #100  
Old 04-22-2014, 07:38 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
Posts: 9,035
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I said I was done posting in this thread but since this is a totally different subject...
The A model RV's (particularly the 7 & 9) can rotate to a higher AOA on the ground. The main gear being farther back on the A model, and the lack of tail wheel, makes it possible.
You can check it your self using the scale 3 view of each model.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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